This invention relates to an improved method of and an apparatus for winding pipes from an elongate strip.
It is now well known to repair conduits by the insertion of a helically wound tube of smaller diameter than the corroded or damaged part. The annular space between the new pipe and the old conduit is filled with grout, usually of a cementitious nature. One of the problems of such a practice is that the finished relined pipe is of smaller diameter than the original conduit. Furthermore, a conduit to be relined is usually out of alignment and has undulations and curves, which means that the relining pipe which is formed must be even smaller in diameter to negotiate such undulations and misalignments.
Also when a hole is formed directly into the soil, the lining of such holes requires a lining pipe of a diameter considerably smaller than the diameter of the hole because of the friction which is generated between the earth and the liner pipe being inserted.
It is already well known to form pipes by winding a ribbed strip of plastics material and joining the edges of convolutions of the strip to progressively form a helically wound tube of the required length. Earlier patents by the same inventor relate to the shape of the strip, the actual form of the strip, the particular jointing means for contiguous edges, the strengthening of the strip by co-wound strengthening members or the like, and to the design of a machine for winding such a strip into a tubular structure.
A tube of this type has to be wound into position in a conduit. One of the special uses and advantages of such a tube is that it can be wound into a conduit by placing the machine into a position at the end of the conduit, which may be below ground, and continuously form the tube and advance it into the conduit for the required distance. Such a system has been used for the relining of sewer pipes and other conduits and in general the tube was grouted into position because it was not possible to wind the tube of a diameter to neatly fit the inner wall of the conduit.
A system was devised by the same inventor known as the xe2x80x9cexpanda pipexe2x80x9d system in which, after forming the tube by winding in the normal manner, and advancing it into the conduit, the tube was expanded to a larger diameter to engage the wall of the conduit. Such a system formed the subject matter of International Patent Application No. PCT/AU87/00069.
While the xe2x80x9cexpanda pipexe2x80x9d system is extremely useful in many applications, it does have some limitations. One limitation is the limit as to the length of pipe that can be produced between joins. This limit arises due to the friction working against rotation of the pipe which, after winding a certain pipe length, becomes too high. The limitations of xe2x80x9cexpanda pipexe2x80x9d become more problematic as the tube diameter increases and cannot be practically accommodated above diameters of about 1 meter. A further limitation of the xe2x80x9cexpanda pipexe2x80x9d system is that a specific type of interlocking rib profile is required that adds to the cost of manufacture.
Conventional conduit relining methods, including the xe2x80x9cexpanda pipexe2x80x9d system, require the conduit to be relined to be out of use, by-passed or xe2x80x9cover pumpedxe2x80x9d. The conduit must be drained of liquids while the relining process is in progress. In many applications this interruption can produce difficulties for sewerage or stormwater system operators.
It is an object of the present invention to provide a method and apparatus that overcomes at least some of the problems of the prior art.
According to a first aspect of the invention there is provided a method of winding a helically wound pipe from a strip having connecting formations spaced apart transversely on the strip and adapted to interlock when the strip is wound in a helical path and adjacent edge portions of the strip overlap one another, said method comprising the steps of:
feeding the strip in a substantially axial direction with respect to the axis of the pipe being wound;
passing the strip between at least one pair of drive rollers located inside of said helical path;
driving the strip around the outside of a plurality of circumferentially spaced guide rollers arranged to form a guide to enable the strip to follow the helical path; and
effecting the interlocking of the adjacent edge portions of the strip relying solely on forces acting on the driven strip and the reactive force provided by tension in adjacent convolution(s) of the strip.
Preferably the radial positions of the guide rollers are adjusted during winding of the strip to thereby vary the circumferential length of the helical pipe being wound.
Preferably the radial positions of the guide rollers are adjusted in unison.
In a further aspect of the invention, there is provided a machine for winding a helically wound pipe from a strip having complementary connecting formations extending along opposite edge portions thereof and which are adapted to interlock when the strip is helically wound comprising:
a frame having at least three circumferentially spaced guide rollers adapted to bear against the inner periphery of the pipe being wound, the rollers forming a guide to a enable the strip to follow a helical path along which the strip is directed when the machine is in use;
strip drive roller means mounted to the frame for driving the strip around the outside of the rollers so as to follow the helical path and cause the adjacent edge portions of adjacent convolutions of the strip to interlock; and
drive means mounted to the frame for driving the strip drive roller means,
characterised in that the strip drive roller means is located wholly inside the helical path and that there is no support means arranged to bear against the outer periphery of the pipe being wound to cause the interlock.
Preferably adjustment means are provided for adjusting the radial positions of the guide rollers.
Preferably further adjustment means are provided for adjusting the angles of the axes of the guide rollers relative to the longitudinal axis of the machine.
The pipe winding machine can either be fixed, with the helical pipe produced exiting from the machine in a continuous process, or can be rotatably movable against the newly formed fixed helical pipe so that it advances axially as the pipe is wound.
Specific embodiments of the invention will now be described in some further detail with reference to and as illustrated in the accompanying figures. These embodiments are illustrative, and are not meant to be restrictive of the scope of the invention.